1. Field of the Invention
The present invention relates to disk drives. More particularly, this invention pertains to a disk drive that includes a vibration damping system having a compressible foam and mass damper fixed adjacent to the outer surface of a printed circuit board for reducing noise and vibration.
2. Description of the Prior Art
Disk drives are commonly employed in workstations, personal computers, portables and other computer systems to store large amounts of data in a readily-available form. Typically, the primary components of a hard disk drive are a head disk assembly and a printed circuit board assembly. When fixed to one another, they form a functional unit for insertion into a bay of a host computer.
The head disk assembly includes a base casting and a cover, a disk having a recording surface, a spindle motor for causing the disk to rotate and an actuator arrangement, driven by a voice coil motor, for advancing a read/write head. A flex circuit transmits data signals to and from the read/write head of the actuator.
The printed circuit board assembly includes circuitry for processing signals and controlling operations of the drive. A representative disk drive incorporating the structures referred to herein is taught, for example, in U.S. Pat. No. 5,790,348 of Alfred et al. entitled "Head Stack Assembly Having a Coil Portion for Damping Vibration Which Includes Elongated Openings in the Plastic Portion." Such patent, property of the assignee herein, is hereby incorporated by reference.
The operation of a hard disk drive necessarily generates structural noise and vibration. Both the electromagnetic spindle and the electromechanical voice coil motors drive the device with the spindle motor continually rotating the storage disk(s) and the voice coil motor selectively driving the actuator(s) to position the read/write heads in the "seek" mode. The motors transmit resonances throughout the disk drive, creating structural vibrations and acoustical, audible noise of varying frequencies. Such noise is transmitted to the substantially-planar printed circuit board which, in turn, can amplify resonant frequency sound intensity, acting, in effect, as a speaker diaphragm.
The presence of acoustic noise in an operating disk drive is undesirable. Customers perceive loudness as an indication of lower quality. As such, acoustic characteristics serve as a benchmark of product quality. Increases in spindle motor speeds intensify the noise transmitted by the head disk assembly to the printed circuit board assembly. Acoustics standards, such as those of the internationally-recognized European International Standards Organization ("ISO"), are regularly lowered, forcing manufacturers to design disk drives characterized by reduced acoustic noise.